feat: TLS1.2 support for RSA-PSS certificates

[lrstewart]

Release Summary:

Added TLS1.2 support for RSA-PSS certificates. Previously, RSA-PSS certificates could only be used with TLS1.3.

Resolved issues:

resolves #4804

Description of changes:

Supporting RSA-PSS certificates with TLS1.2 turned out to be as simple as just removing the TLS1.3-only restrictions. Previously, we specifically restricted RSA-PSS-PSS to TLS1.3.

Call-outs:

• Is this a feature or a fix? 🤔

Testing:

I added a new end-to-end test to clearly assert that we support all certificates where we expect to.

I also updated the integration tests to use TLS1.2 + RSA-PSS. It's hard to tell that's working, so I dumped the output of a successful test_s2n_client_signature_algorithms run into a file and searched it. It looks like:

...
293: PASSED test_signature_algorithms.py::test_s2n_client_signature_algorithms[no-client-auth-rsa_pss_pss_sha256-RSA_PSS_2048_SHA256-TLS1.2-S2N-OpenSSL-ECDHE-RSA-AES128-GCM-SHA256]
293: PASSED test_signature_algorithms.py::test_s2n_client_signature_algorithms[no-client-auth-rsa_pss_pss_sha256-RSA_PSS_2048_SHA256-TLS1.2-S2N-OpenSSL-ECDHE-RSA-AES256-GCM-SHA384]
293: PASSED test_signature_algorithms.py::test_s2n_client_signature_algorithms[no-client-auth-rsa_pss_pss_sha256-RSA_PSS_2048_SHA256-TLS1.2-S2N-OpenSSL-ECDHE-RSA-CHACHA20-POLY1305]
...

The commands I ran, and the results:

$ cat signature_algorithms.out | grep ": PASSED " | grep pss_pss | wc -l
40

$ cat signature_algorithms.out | grep ": PASSED " | grep pss_pss | grep TLS1.2 | wc -l
28

$ cat signature_algorithms.out | grep ": PASSED " | grep pss_pss | grep TLS1.2 | grep s2n_client | wc -l
14

$ cat signature_algorithms.out | grep ": PASSED " | grep pss_pss | grep TLS1.2 | grep s2n_server | wc -l
14

$ cat signature_algorithms.out | grep ": PASSED " | grep pss_pss | sed 's/^.*-OpenSSL-\(.*\)\]/\1/' | sort -u
ECDHE-RSA-AES128-GCM-SHA256
ECDHE-RSA-AES128-SHA
ECDHE-RSA-AES128-SHA256
ECDHE-RSA-AES256-GCM-SHA384
ECDHE-RSA-AES256-SHA
ECDHE-RSA-AES256-SHA384
ECDHE-RSA-CHACHA20-POLY1305
TLS_AES_128_GCM_SHA256
TLS_AES_256_GCM_SHA384
TLS_CHACHA20_POLY1305_SHA256

That looks correct to me, given the full set of ciphers:

$ cat signature_algorithms.out | grep ": PASSED " | grep "OpenSSL" | sed 's/^.*-OpenSSL-\(.*\)\]/\1/' | sort -u
AES128-SHA
AES128-SHA256
AES256-SHA
AES256-SHA256
DHE-RSA-AES128-GCM-SHA256
DHE-RSA-AES128-SHA
DHE-RSA-AES128-SHA256
DHE-RSA-AES256-GCM-SHA384
DHE-RSA-AES256-SHA
DHE-RSA-AES256-SHA256
DHE-RSA-CHACHA20-POLY1305
ECDHE-ECDSA-AES128-GCM-SHA256
ECDHE-ECDSA-AES128-SHA
ECDHE-ECDSA-AES128-SHA256
ECDHE-ECDSA-AES256-GCM-SHA384
ECDHE-ECDSA-AES256-SHA
ECDHE-ECDSA-AES256-SHA384
ECDHE-ECDSA-CHACHA20-POLY1305
ECDHE-RSA-AES128-GCM-SHA256
ECDHE-RSA-AES128-SHA
ECDHE-RSA-AES128-SHA256
ECDHE-RSA-AES256-GCM-SHA384
ECDHE-RSA-AES256-SHA
ECDHE-RSA-AES256-SHA384
ECDHE-RSA-CHACHA20-POLY1305
TLS_AES_128_GCM_SHA256
TLS_AES_256_GCM_SHA384
TLS_CHACHA20_POLY1305_SHA256

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.